SOX10 Is a Useful Marker for Triple Negative Breast Cancer

Abstract

Triple negative breast cancers (TNBCs) are often aggressive neoplasms that are poorly differentiated, making confirmation that a metastasis is from a TNBC challenging. Many immunohistochemical (IHC) breast markers are specific but not sensitive, particularly in TNBCs. SOX10 is a nuclear transcription factor that is primarily used in diagnosing neuroectodermal tumors but that has also been shown to be expressed in benign breast tissue and some breast cancers. The aim of this study is to characterize SOX10 expression in TNBC and compare with other known IHC markers. Sections from tissue microarrays (TMAs) were constructed from 135 TNBCs using 0.2 cm cores in triplicate. Relevant pathologic data were recorded. TMAs were stained with SOX10, GATA3, GCDFP-15, and mammaglobin. Each stain was scored by the percent positive cells (0%, negative; <10%, focal; 10%-70%, patchy; >70%, diffuse) and intensity (weak, moderate or strong). >10% staining in tumor cells was considered positive. Overall, SOX10 was positive in 59% of TNBCs and showed a strong diffuse staining pattern in 50%. 41% of TNBCs were completely negative for SOX10 compared with 58% for mammaglobin, 81% for GCDFP-15, and 93% for GATA3. The strong, diffuse staining seen with SOX10 was uncommon with the other 3 markers (only 2%-10% showed diffuse staining). In conclusion, SOX10 was positive in a higher percentage of TNBC and was more likely to exhibit strong diffuse positivity when compared to commonly used breast markers mammaglobin, GCDFP-15, and GATA3. These results suggest that SOX10 could be useful when included in a panel of markers to diagnose TNBC, especially in the setting of metastatic disease.